UPD EEE 113 Communications Online Quiz on Channel Effects (2025-2026 First Semester)

This worksheet is an unlimited-attempt review material that features channel effects. Below, there is a combination of multiple-choice, true-or-false, and cloze items. Due to the interactive nature of this page, this worksheet can’t be printed out directly; no data will be uploaded by filling in this worksheet.

Questions

1. An LTI system models the following effects: attenuation, delay, offset, and blurring of transitions offset, and blurring of transitions delay, and offset delay, and blurring of transitions
2. Suppose we transmit binary bits over a given LTI channel using two different communication protocols. Protocol A uses a bit time of 5 microseconds, and protocol B uses a bit time of 20 microseconds. If all other aspects of the protocols are the same, then Protocol B will have less ISI.
3. If a shorter bit time was used, bit rate increases decreases and BER increases decreases
4. Which of the following media does not occupy the electromagnetic radio spectrum: Bluetooth Wi-Fi fibre optic LTE FM / AM
5. Which of the following statements about equalization is FALSE? If the channel is fast, it gives more weight to the current received signal.If the channel is slow, it gives more weight to the change in symbols.It can help reduce noise.It can help minimize intersymbol interference (ISI).
6. Which of the following statements about the channel is FALSE?Equalization can minimize the band-limited effects of the channel.The recursive model used in equalization is equivalent to the exponential step response model.A channel’s step response is always of the exponential form s(n) = k(1 - a^(n + 1) * u (n)The band-limited effects of the channel is due to its frequency response.
7. Given the recursive channel model:

   $y\left(n\right)=.3y(n-1)+.21x\left(n\right)$

   where $y(-1)=0$, what's the equivalent step response:
   • $s\left(n\right)=0.7(1-{0.21}^{n+1})u\left(n\right)$
   • $s\left(n\right)=0.21(1-{0.3}^{n+1})u\left(n\right)$
   • $s\left(n\right)=0.3(1-{0.3}^{n+1})u\left(n\right)$
   • $s\left(n\right)=0.3(1-{0.7}^{n+1})u\left(n\right)$
   • $s\left(n\right)=0.7(1-{0.3}^{n+1})u\left(n\right)$
8. Given the same recursive channel model from the previous item, what is the value of the y(n) at n = 5 if input signal is $x\left(n\right)=u\left(n\right)-u(n-7)$?
9. Assuming that a laptop's average power consumption is 33 watts and that it is powered a 11.1V, 4400 mAh, 49 Wh battery, how long do you predict the laptop would operate for if the battery starts out fully charged? 1.48 4.9 4.4 15 hours
10. A communication receiver works properly if the minimum signal-to-noise ratio is 20 dB. What should be the minimum signal power in Watts if the received noise power is 0.01 W?
11. Channel coding protects the signal (and information) by adding redundancy bits. Hence, it decreases the data rate.
12. The bit sequence from an ADC source comes at a bit rate of 363 kbps. The channel coder receives the ADC output, and implements a (9, 8, 2) block code before transmission. What is the required sampling rate (in MHz) at the transmitter if the output of the channel coder is sampled at 4 samples per bit?

Markscheme

1. attenuation, delay, and blurring of transitions
3. 1. increases
   2. increases
4. fibre optic
6. A channel’s step response is always of the exponential form $s\left(n\right)=k(1-a^{n+1})u\left(n\right)$
7. $s\left(n\right)=0.3(1-{0.3}^{n+1})u\left(n\right)$
9. 1.48
10. 1
12. 1.6335